Cultured Y-1 mouse adrenal tumor cells have been shown to respond to ACTH and cAMP like normal adrenal cells. After many passages in culture these cells lose the ability to produce steroids. This project seeks to isolate and characterize the cell surface ACTH receptor and also the cytoplasmic microfilament network associated with the receptors. Having developed proceedures for isolating the microfilament in stimulated and non-stimulated adrenal cells, we are proceeding to characterize difference in these 2 cell forms. We are also proceeding with similar examinations in older cells. We anticipate specific radioiodination of the ACTH receptor and plan to develop techniques to isolate this structure. Having isolated the receptor the techniques will be utilized to isolate the receptors of older cells in order that we can compare them. Finally, we plan to determine whether there is any indentifiable association between the receptor structure in the membrane and the cytoplasmic microfilaments. Should an association exist, we plan to examine it in young and old cells.